The volcano under Lake Ilopango exploded around 536 A.D., sending so much ash into the atmosphere it blanketed much of the planet – reaching as far as Europe and Asia – for two years, killing crops and cooling the Earth.

“By any measure, [it was] one of the five largest volcanic eruption on Earth in the last 10,000 years,” says Dull, a Senior Research Fellow in paleontology, paleoclimatology and paleo-hazard at the University of Texas at Austin.

The explosion, he says, coincides perfectly with historic ecological events, in particular the cooling of the Earth.

But he still needed something that tied it all together.

That turned out to be a tree preserved by volcanic ash for almost 1500 years.

“We had this perfect time capsule — a tree killed by the eruption and snapped in place,” he explains. “Fine ash fell around it like snow and entombed it.”

From there Dull and other scientists began connecting the dots, from the first recorded outbreak of the Bubonic plague — which lead to 50 million deaths – as well as the fall of the Roman Empire.

The discovery was profiled for History’s series Perfect Storms – a program looking at extreme weather phenomena.

The show’s senior producer Steve Gamester said large-scale natural events that happen on one side of the world can have major consequences on the other.

“We see that today with natural disasters [such as] the tsunami that hit Japan. That had a global impact on economy and trade,” he explains.

Another example would be the eruption of Eyjafjallajökull in 2010 – the Icelandic volcano that spewed ash for weeks, disrupting flights worldwide.

That eruption wasn’t nearly as significant as Ilopongo, but that doesn’t mean we’re not due for another major volcanic event.

In fact, Dull believes we’re overdue: the last major eruption that was remotely close to the same size was Mount Tambora, in Indonesia, in 1815.

More study is needed to determine if the Ilopongo volcanic explosion indeed triggered the chain of events that led to Dark Ages. But, for the first time, scientists have hard evidence of what could be the first link.